What are the brown growths in my ash tree?

Question:

What are the brown growths in my ash tree?

Answer:

The brown growths in your ash tree are probably ash flower galls.  Galls are abnormal plant growths induced to form by small insects, mites, or other organisms.  On ash trees, a tiny mite causes the male flowers to develop into roundish, green, 1-inch growths.  In late summer/early fall, the growths turn dark brown and become woody. 

While ash flower galls are unsightly, they do no seriously harm healthy trees.  Control treatments are usually not practical nor necessary.